Dual Color SMD LED LTST-C155TBKFKT Datasheet - Blue & Orange - 20mA & 30mA - English Technical Document

1. Product Overview

This document details the specifications for a dual-color, surface-mount device (SMD) LED. The component integrates two distinct semiconductor chips within a single package: an InGaN (Indium Gallium Nitride) chip emitting blue light and an AlInGaP (Aluminum Indium Gallium Phosphide) chip emitting orange light. This design allows for the creation of two independent light sources or, through controlled driving, potential color mixing in applications. The LED is packaged in tape and reel format compatible with automated pick-and-place assembly systems, adhering to EIA standard packaging. It is designed as a RoHS-compliant and green product.

1.1 Core Features and Target Applications

The primary advantage of this LED is its dual-color capability in a compact SMD footprint. Key features include ultra-high brightness from both chip technologies, compatibility with infrared (IR) and vapor phase reflow soldering processes, and design for integration with automated assembly equipment. Its I.C. compatibility indicates it can be driven directly by standard logic-level signals with appropriate current limiting. Typical applications include status indicators, backlighting for switches and panels, decorative lighting, and consumer electronics where space is at a premium and multiple indication colors are required from a single component location.

2. Absolute Maximum Ratings

Operating or storing the device beyond these limits may cause permanent damage.

• Power Dissipation: Blue: 76 mW, Orange: 75 mW (at Ta=25°C)
• Peak Forward Current: Blue: 100 mA, Orange: 80 mA (1/10 duty cycle, 0.1ms pulse width)
• DC Forward Current: Blue: 20 mA, Orange: 30 mA
• Derating: Blue: 0.25 mA/°C, Orange: 0.4 mA/°C (linear from 25°C)
• Reverse Voltage: 5 V for both colors (Note: Cannot be continuously operated in reverse bias)
• Operating & Storage Temperature Range: -55°C to +85°C
• Soldering Temperature: Wave/IR: 260°C for 5 seconds max; Vapor Phase: 215°C for 3 minutes max.

3. Electrical and Optical Characteristics

Measured at an ambient temperature (Ta) of 25°C under specified test conditions.

3.1 Optical Parameters (at IF=20mA)

• Luminous Intensity (Iv):
  
  Blue: Min. 28.0 mcd, Typ. 45.0 mcd.
  
  Orange: Min. 45.0 mcd, Typ. 90.0 mcd.
  
  Measured with a sensor/filter approximating the CIE photopic eye-response curve.
• Viewing Angle (2θ1/2): Typical 130 degrees for both colors. This is the full angle at which intensity drops to half its on-axis value.
• Peak Wavelength (λP): Blue: Typ. 468 nm, Orange: Typ. 611 nm.
• Dominant Wavelength (λd): Blue: Typ. 470 nm, Orange: Typ. 605 nm. Derived from the CIE chromaticity diagram, this defines the perceived color.
• Spectral Bandwidth (Δλ): Blue: Typ. 25 nm, Orange: Typ. 17 nm.

3.2 Electrical Parameters

• Forward Voltage (VF) at IF=20mA:
  
  Blue: Min. 2.80V, Typ. 3.50V, Max. 3.80V.
  
  Orange: Min. 1.80V, Typ. 2.00V, Max. 2.40V.
• Reverse Current (IR): Max. 10 μA for both at VR=5V.
• Capacitance (C): Typical 40 pF for Orange at VF=0V, f=1MHz.

4. Binning System

The LEDs are sorted into bins based on luminous intensity to ensure consistency within a production lot.

4.1 Luminous Intensity Binning

Blue Chip (@20mA):

Code N: 28.0 - 45.0 mcd

Code P: 45.0 - 71.0 mcd

Code Q: 71.0 - 112.0 mcd

Code R: 112.0 - 180.0 mcd

Orange Chip (@20mA):

Code P: 45.0 - 71.0 mcd

Code Q: 71.0 - 112.0 mcd

Code R: 112.0 - 180.0 mcd

Tolerance within each intensity bin is +/-15%.

5. Performance Curve Analysis

The datasheet references typical characteristic curves which would normally illustrate the relationship between key parameters. Designers should consider these non-linear relationships.

5.1 Forward Current vs. Forward Voltage (I-V Curve)

Both LEDs exhibit a diode-like exponential I-V characteristic. The Blue (InGaN) LED has a significantly higher typical forward voltage (~3.5V) compared to the Orange (AlInGaP) LED (~2.0V) at 20mA. This voltage difference is critical for circuit design, especially when driving both colors from a common voltage rail, as it necessitates different series resistor values to achieve the same target current.

5.2 Luminous Intensity vs. Forward Current

Luminous intensity is approximately proportional to forward current within the recommended operating range. However, efficiency may drop at very high currents due to increased heat. The derating specifications (0.25 mA/°C for Blue, 0.4 mA/°C for Orange) indicate how the maximum allowable DC current must be reduced as ambient temperature rises above 25°C to prevent overheating and ensure longevity.

5.3 Spectral Distribution

The Blue chip emits in the ~468-470 nm range with a relatively broad spectral bandwidth of 25 nm (Typ.). The Orange chip emits in the ~605-611 nm range with a narrower bandwidth of 17 nm (Typ.). The dominant wavelength values are crucial for color-critical applications.

6. Mechanical and Packaging Information

6.1 Pin Assignment and Polarity

The device has four pins. For the LTST-C155TBKFKT variant:

- The InGaN Blue chip is connected to pins 1 and 3.

- The AlInGaP Orange chip is connected to pins 2 and 4.

This configuration typically allows for independent control of each color. The lens is water clear.

6.2 Package Dimensions and Tape/Reel

The LED is supplied in 8mm wide embossed carrier tape on 7-inch (178mm) diameter reels. Standard reel quantity is 4000 pieces. The datasheet includes detailed dimensional drawings for the LED body, recommended solder pad layout (land pattern), and the tape & reel specifications, which are in accordance with ANSI/EIA 481-1-A-1994. All dimensions are in millimeters with a standard tolerance of ±0.10 mm unless otherwise specified. Proper pad design is essential for reliable soldering and mechanical stability.

7. Soldering and Assembly Guidelines

7.1 Reflow Soldering Profiles

The component is compatible with standard reflow processes. Two suggested infrared (IR) reflow profiles are provided: one for normal (tin-lead) solder process and one for Pb-free (e.g., SnAgCu) solder process. Critical parameters include:

- Pre-heat: Ramp-up to 120-150°C.

- Soak/Pre-heat Time: Maximum 120 seconds.

- Peak Temperature: Maximum 260°C.

- Time Above Liquidus: 5 seconds maximum at peak temperature.

Adherence to these profiles prevents thermal shock and damage to the LED package or die.

7.2 Wave and Hand Soldering

For wave soldering, pre-heat should not exceed 100°C for a maximum of 60 seconds, with the solder wave at a maximum of 260°C for up to 10 seconds. If hand soldering with an iron is necessary, the tip temperature should not exceed 300°C, and contact time should be limited to 3 seconds per joint, for one time only, to prevent excessive heat transfer.

7.3 Cleaning and Storage

Cleaning: Only specified cleaning agents should be used. Isopropyl alcohol or ethyl alcohol at normal temperature for less than one minute is recommended. Unspecified chemicals may damage the epoxy lens or package.

Storage: For long-term storage outside the original moisture-barrier bag, LEDs should be kept in an environment not exceeding 30°C and 70% relative humidity. For extended storage, use a sealed container with desiccant or a nitrogen ambient. Components exposed to ambient air for more than one week should be baked at approximately 60°C for at least 24 hours before soldering to remove absorbed moisture and prevent \"popcorning\" during reflow.

8. Application Design Considerations

8.1 Drive Circuit Design

LEDs are current-operated devices. To ensure uniform brightness and prevent damage, a current-limiting mechanism is mandatory. The recommended circuit (Circuit A) uses a series resistor for each LED. The resistor value (R) is calculated using Ohm's Law: R = (V_supply - V_F_LED) / I_F, where V_F_LED is the forward voltage of the specific LED at the desired current I_F. Due to the variance in V_F (see binning and typical ranges), driving multiple LEDs in parallel from a single voltage source with a shared resistor (Circuit B) is not recommended, as it can lead to significant current imbalance and uneven brightness.

8.2 Electrostatic Discharge (ESD) Protection

The LED is sensitive to electrostatic discharge and voltage surges. Precautions must be taken during handling and assembly:

- Use grounded wrist straps or anti-static gloves.

- Ensure all workstations, tools, and equipment are properly grounded.

- Implement ESD-safe packaging and transportation procedures.

Failure to observe ESD precautions can lead to immediate failure or latent damage that reduces long-term reliability.

8.3 Thermal Management

While the power dissipation is relatively low, proper thermal design extends lifespan and maintains optical performance. The derating curves specify how maximum current must decrease with rising ambient temperature. Ensuring adequate copper area on the PCB around the LED's thermal pads (if any) or vias to inner layers can help dissipate heat, especially in high-ambient-temperature or enclosed applications.

9. Technical Comparison and Differentiation

This dual-color LED's primary differentiation lies in its two distinct, high-brightness chips in one standard SMD package. Compared to using two separate single-color LEDs, it saves PCB space, reduces component count, and simplifies pick-and-place assembly. The use of InGaN for blue offers higher efficiency and brightness than older technologies like GaP. The AlInGaP technology for orange provides high efficiency and excellent color purity in the red-orange-amber spectrum. The combination allows for design flexibility in status indication (e.g., blue for standby, orange for active/fault) or simple color blending.

10. Frequently Asked Questions (FAQ)

Q1: Can I drive both the blue and orange LEDs simultaneously at their full rated current?

A1: The Absolute Maximum Ratings are specified per chip. The total power dissipation for the package would be the sum of the dissipation from each active chip. You must ensure the combined thermal load does not exceed the package's ability to dissipate heat, especially at high ambient temperatures. Consult the derating specifications.

Q2: Why are the forward voltages so different between the blue and orange chips?

A2: The forward voltage is a fundamental property of the semiconductor material's bandgap. InGaN (blue) has a wider bandgap (~3.4 eV) than AlInGaP (orange/red, ~2.0 eV), which directly results in a higher forward voltage required to achieve conduction and light emission.

Q3: What is the difference between peak wavelength and dominant wavelength?

A3: Peak wavelength (λP) is the wavelength at which the spectral power distribution is maximum. Dominant wavelength (λd) is the single wavelength of a monochromatic light that would appear to have the same color as the LED's output when compared to a standard white reference. For LEDs with a symmetric spectrum, they are often close. For skewed spectra, λd is more representative of the perceived color.

Q4: How do I interpret the intensity bin codes when ordering?

A4: The bin code (e.g., N, P, Q, R) defines a guaranteed minimum and maximum luminous intensity range for the LED at the test current. Specifying a bin code ensures you receive LEDs with consistent brightness within that range. For example, ordering from Bin \"P\" for the orange chip guarantees an intensity between 45.0 and 71.0 mcd at 20mA.

11. Design and Usage Case Study

Scenario: Dual-Status Indicator for a Network Router

A designer needs two status indications (\"Power On/Standby\" and \"Network Activity\") but has space for only one LED indicator hole on the front panel. Using the LTST-C155TBKFKT provides an elegant solution.

Implementation: The blue LED is connected to the \"Power\" signal via a current-limiting resistor calculated for 15mA (e.g., R = (3.3V - 3.5V)/0.015A, requiring a slight adjustment to supply voltage or resistor value based on typical Vf). The orange LED is connected to a pulse signal from the network controller, blinking to indicate data activity. The microcontroller firmware can be programmed to also use both LEDs for a third state (e.g., solid orange for a fault condition). This single component fulfills multiple roles, saving space, assembly cost, and simplifying the bill of materials compared to a two-LED solution.

12. Technology Principles

Light emission in these LEDs is based on electroluminescence in direct bandgap semiconductor materials. When a forward voltage is applied across the p-n junction, electrons and holes are injected into the active region where they recombine. The energy released during recombination is emitted as a photon. The wavelength (color) of this photon is determined by the bandgap energy (Eg) of the semiconductor material, according to the equation λ ≈ 1240/Eg (nm), where Eg is in electron-volts (eV). InGaN materials are used for shorter wavelengths (blue, green, white), while AlInGaP materials are used for longer wavelengths (yellow, orange, red). The \"water clear\" lens is typically made of epoxy or silicone that is transparent to the emitted wavelengths.

13. Industry Trends

The trend in SMD indicator LEDs continues toward higher efficiency (more light output per unit of electrical power), smaller package sizes, and increased integration. Dual- and multi-color LEDs in single packages are becoming more common to support complex status indication and miniaturization. There is also a strong drive for improved reliability under harsh conditions (higher temperature, humidity) and compatibility with lead-free (Pb-free) and high-temperature soldering processes required by modern electronics manufacturing. Furthermore, the demand for precise color consistency and tighter binning tolerances is growing for applications in automotive interiors, consumer appliances, and professional equipment where brand identity and user experience are tied to precise visual cues.